diff --git a/app.py b/app.py
index 2d17b5c..5ec4089 100644
--- a/app.py
+++ b/app.py
@@ -95,8 +95,14 @@ def create_app(config_object="config"):
             .filter(Battery.storage_location.isnot(None))
             .distinct().order_by(Battery.storage_location).all()
         ]
+        brand_counts = {
+            r[0]: r[1]
+            for r in db.query(Battery.brand, func.count(Battery.id))
+                       .group_by(Battery.brand).all()
+        }
         return render_template("battery_add.html", form_count=1, brands=brands,
-                               storage_locations=storage_locations)
+                               storage_locations=storage_locations,
+                               brand_counts=brand_counts)
 
     # ------------------------------------------------------------------ #
     # Battery — detail
diff --git a/templates/base.html b/templates/base.html
index a373208..97a5ea9 100644
--- a/templates/base.html
+++ b/templates/base.html
@@ -56,6 +56,13 @@
       --count-retired:   #64748b;
     }
 
+    /* Confirmation modal */
+    #confirm-modal { display:none; position:fixed; inset:0; z-index:1000; background:rgba(0,0,0,.45); align-items:center; justify-content:center; }
+    #confirm-modal.open { display:flex; }
+    #confirm-modal-box { background:var(--bg-card); border-radius:8px; padding:1.5rem; max-width:400px; width:calc(100% - 2rem); box-shadow:0 8px 24px rgba(0,0,0,.25); }
+    #confirm-modal-msg { margin-bottom:1.25rem; color:var(--text-body); font-size:0.95rem; line-height:1.5; }
+    #confirm-modal-actions { display:flex; gap:0.75rem; justify-content:flex-end; }
+
     /* ─── Dark mode variables ────────────────────────────────────────── */
     @media (prefers-color-scheme: dark) {
       :root {
@@ -326,10 +333,62 @@
 
     {% block content %}{% endblock %}
   </div>
+  <div id="confirm-modal" role="dialog" aria-modal="true">
+    <div id="confirm-modal-box">
+      <p id="confirm-modal-msg"></p>
+      <div id="confirm-modal-actions">
+        <button id="confirm-modal-cancel" class="btn btn-secondary">Cancel</button>
+        <button id="confirm-modal-ok" class="btn btn-danger">Confirm</button>
+      </div>
+    </div>
+  </div>
+
   <script>
     if ('serviceWorker' in navigator) {
       navigator.serviceWorker.register('/sw.js');
     }
+
+    (function() {
+      var modal     = document.getElementById('confirm-modal');
+      var msgEl     = document.getElementById('confirm-modal-msg');
+      var okBtn     = document.getElementById('confirm-modal-ok');
+      var cancelBtn = document.getElementById('confirm-modal-cancel');
+      var _cb = null;
+
+      window.showConfirm = function(msg, onOk, okLabel, okClass) {
+        msgEl.textContent = msg;
+        okBtn.textContent = okLabel || 'Confirm';
+        okBtn.className = 'btn ' + (okClass || 'btn-danger');
+        modal.classList.add('open');
+        _cb = onOk;
+        cancelBtn.focus();
+      };
+
+      function closeModal() { modal.classList.remove('open'); _cb = null; }
+
+      okBtn.addEventListener('click', function() {
+        var cb = _cb; closeModal(); if (cb) cb();
+      });
+      cancelBtn.addEventListener('click', closeModal);
+      modal.addEventListener('click', function(e) { if (e.target === modal) closeModal(); });
+      document.addEventListener('keydown', function(e) {
+        if (e.key === 'Escape' && modal.classList.contains('open')) closeModal();
+      });
+
+      // Global handler: forms with data-confirm attribute
+      document.addEventListener('submit', function(e) {
+        var form = e.target;
+        var msg = form.dataset.confirm;
+        if (!msg || form.dataset.confirmed) return;
+        e.preventDefault();
+        var okLabel = form.dataset.confirmOk || 'Confirm';
+        var okClass = form.dataset.confirmClass || 'btn-danger';
+        window.showConfirm(msg, function() {
+          form.dataset.confirmed = '1';
+          form.submit();
+        }, okLabel, okClass);
+      });
+    }());
   </script>
 </body>
 </html>
diff --git a/templates/battery_add.html b/templates/battery_add.html
index be3a4b9..c187b43 100644
--- a/templates/battery_add.html
+++ b/templates/battery_add.html
@@ -27,6 +27,7 @@
         <label for="count">Quantity</label>
         <input type="number" id="count" name="count" value="{{ form_count|default(1) }}" min="1" max="50">
         <small class="text-muted">Labels are auto-generated (e.g. Eneloop 001, Eneloop 002)</small>
+        <div id="label-preview" style="font-size:0.85rem;color:var(--link);margin-top:0.3rem;font-weight:500;min-height:1.2em;"></div>
       </div>
 
       <div class="form-group">
@@ -96,6 +97,8 @@
 </div>
 
 <script>
+var brandCounts = {{ brand_counts|default({})|tojson }};
+
 function metaSelectChanged(sel, inputId) {
   var input = document.getElementById(inputId);
   if (sel.value === '__new__') {
@@ -106,8 +109,26 @@ function metaSelectChanged(sel, inputId) {
     input.style.display = 'none';
     input.value = sel.value;
   }
+  if (inputId === 'brand') updateLabelPreview();
 }
 
+function updateLabelPreview() {
+  var brand = document.getElementById('brand').value.trim();
+  var count = parseInt(document.getElementById('count').value, 10) || 1;
+  var preview = document.getElementById('label-preview');
+  if (!brand) { preview.textContent = ''; return; }
+  var existing = brandCounts[brand] !== undefined ? brandCounts[brand] : 0;
+  var first = existing + 1;
+  var last  = existing + count;
+  var pad = function(n) { return n.toString().padStart(3, '0'); };
+  preview.textContent = count === 1
+    ? 'Will create: ' + brand + ' ' + pad(first)
+    : 'Will create: ' + brand + ' ' + pad(first) + ' \u2192 ' + brand + ' ' + pad(last);
+}
+
+document.getElementById('count').addEventListener('input', updateLabelPreview);
+document.getElementById('brand').addEventListener('input', updateLabelPreview);
+
 // Restore brand state on error re-render
 (function () {
   var input = document.getElementById('brand');
diff --git a/templates/battery_detail.html b/templates/battery_detail.html
index 0db404f..d469cd4 100644
--- a/templates/battery_detail.html
+++ b/templates/battery_detail.html
@@ -114,7 +114,7 @@
           <td data-label="">
             <form class="inline" method="post"
                   action="{{ url_for('battery_capacity_test_delete', battery_id=battery.id, test_id=t.id) }}"
-                  onsubmit="return confirm('Delete this test record?')">
+                  data-confirm="Delete this test record?" data-confirm-ok="Delete">
               <button class="btn btn-sm btn-danger" type="submit">Delete</button>
             </form>
           </td>
@@ -172,7 +172,7 @@
           <td data-label="">
             <form class="inline" method="post"
                   action="{{ url_for('battery_charge_log_delete', battery_id=battery.id, log_id=log.id) }}"
-                  onsubmit="return confirm('Delete this charge log entry?')">
+                  data-confirm="Delete this charge log entry?" data-confirm-ok="Delete">
               <button class="btn btn-sm btn-danger" type="submit">Delete</button>
             </form>
           </td>
diff --git a/templates/dashboard.html b/templates/dashboard.html
index 9fc6f04..5f8543c 100644
--- a/templates/dashboard.html
+++ b/templates/dashboard.html
@@ -80,8 +80,8 @@
       <span id="selected-count" style="font-size:0.85rem;color:#64748b;margin-right:0.25rem;"></span>
       <button class="btn btn-sm btn-warning" name="action" value="unassign" type="submit">Unassign</button>
       <button class="btn btn-sm btn-secondary" name="action" value="retire" type="submit">Retire</button>
-      <button class="btn btn-sm btn-danger" name="action" value="delete" type="submit"
-              onclick="return confirm('Permanently delete selected batteries?')">Delete</button>
+      <button class="btn btn-sm btn-danger" name="action" value="delete" type="button"
+              onclick="bulkActionConfirm(this, 'Permanently delete selected batteries?', 'Delete', 'btn-danger')">Delete</button>
       <span style="display:flex;gap:0.35rem;align-items:center;flex-wrap:wrap;">
         <input type="hidden" name="field_name" id="bulk-field-name" value="storage_location">
         <select id="bulk-field-select" onchange="updateBulkField(this)"
@@ -121,8 +121,8 @@
           <option value="{{ d.id }}">{{ d.name }} ({{ d.installed_count() }}/{{ d.battery_slots }})</option>
           {% endfor %}
         </select>
-        <button class="btn btn-sm btn-primary" name="action" value="install_device" type="submit"
-                onclick="return confirmInstallDevice()">Install in device</button>
+        <button class="btn btn-sm btn-primary" name="action" value="install_device" type="button"
+                onclick="confirmInstallDevice(this)">Install in device</button>
       </span>
       <span style="display:flex;gap:0.35rem;align-items:center;flex-wrap:wrap;">
         <input type="date" name="charged_date" id="bulk-charged-date"
@@ -278,21 +278,36 @@ function applyFilters() {
   updateToolbar();
 }
 
-function confirmInstallDevice() {
+function confirmInstallDevice(btn) {
   var deviceSel = document.getElementById('bulk-device-select');
-  if (!deviceSel.value) { deviceSel.focus(); return false; }
+  if (!deviceSel.value) { deviceSel.focus(); return; }
   var movers = Array.prototype.filter.call(
     document.querySelectorAll('.row-cb:checked'),
     function(cb) { return cb.closest('tr').dataset.status === 'installed'; }
   );
   if (movers.length > 0) {
     var n = movers.length;
-    return confirm(
+    showConfirm(
       n + ' selected batter' + (n === 1 ? 'y is' : 'ies are') +
-      ' already installed elsewhere. Unassign and move to the selected device?'
+      ' already installed elsewhere. Unassign and move to the selected device?',
+      function() { submitWithAction(btn); },
+      'Move', 'btn-warning'
     );
+  } else {
+    submitWithAction(btn);
   }
-  return true;
+}
+
+function bulkActionConfirm(btn, msg, okLabel, okClass) {
+  showConfirm(msg, function() { submitWithAction(btn); }, okLabel, okClass);
+}
+
+function submitWithAction(btn) {
+  var form = btn.form || document.getElementById('bulk-form');
+  var inp = document.createElement('input');
+  inp.type = 'hidden'; inp.name = btn.name; inp.value = btn.value;
+  form.appendChild(inp);
+  form.submit();
 }
 
 function quickAssign(action, batteryId) {
diff --git a/templates/device_list.html b/templates/device_list.html
index c4cedf2..49ef61c 100644
--- a/templates/device_list.html
+++ b/templates/device_list.html
@@ -59,12 +59,14 @@
             <a class="btn btn-sm btn-secondary" href="{{ url_for('device_detail', device_id=d.id) }}">View</a>
             {% if d.installed_count() > 0 %}
             <form class="inline" method="post" action="{{ url_for('device_unassign_all', device_id=d.id) }}"
-                  onsubmit="return confirm('Unassign all batteries from {{ d.name }}?')">
+                  data-confirm="Unassign all batteries from {{ d.name }}?"
+                  data-confirm-ok="Unassign" data-confirm-class="btn-warning">
               <button class="btn btn-sm btn-warning" type="submit">Unassign All</button>
             </form>
             {% endif %}
             <form class="inline" method="post" action="{{ url_for('device_delete', device_id=d.id) }}"
-                  onsubmit="return confirm('Delete {{ d.name }}? All installed batteries will be unassigned.');">
+                  data-confirm="Delete {{ d.name }}? All installed batteries will be unassigned."
+                  data-confirm-ok="Delete" data-confirm-class="btn-danger">
               <button class="btn btn-sm btn-danger" type="submit">Delete</button>
             </form>
           </td>
diff --git a/tests/test_acceptance.py b/tests/test_acceptance.py
index 42b43c5..f21e394 100644
--- a/tests/test_acceptance.py
+++ b/tests/test_acceptance.py
@@ -41,6 +41,24 @@ def test_dashboard_loads(seeded_client):
     assert b"BrandX 002" in resp.data
 
 
+# ------------------------------------------------------------------ #
+# Battery add — label preview data
+# ------------------------------------------------------------------ #
+
+def test_battery_add_get_renders(client):
+    resp = client.get("/battery/add")
+    assert resp.status_code == 200
+    assert b"brandCounts" in resp.data
+
+
+def test_battery_add_brand_counts_reflects_existing(seeded_client):
+    # seeded_client has BrandX x2, BrandY x1
+    resp = seeded_client.get("/battery/add")
+    assert resp.status_code == 200
+    assert b'"BrandX": 2' in resp.data or b'"BrandX":2' in resp.data
+    assert b'"BrandY": 1' in resp.data or b'"BrandY":1' in resp.data
+
+
 # ------------------------------------------------------------------ #
 # Battery — bulk add
 # ------------------------------------------------------------------ #